Have you been wondering why your gardening has been a disaster this year? You're not on your own.

Food prices are set to rise after a summer of wet weather has hit harvests. The global price of wheat has risen by 30% over the last year. Potato harvests are down by half in some areas. The NFU's Scottish cereal survey indicated wheat yield was down by 18% from 2011, winter barley yield down 7%, spring barley yield down 18% and winter oilseed rape yield down 26%.

Apple growers in England say it's the worst harvest for 12 years and Save the Children reports that food price rises and volatility are the "new normal". Shoppers will be affected by higher prices for other crops, with global grain costs hit by American drought and Russian heatwave. The yo-yo flood and drought reflects a society not sure where or how to live and now unable to feed itself properly.

This isn't the exaggeration of green miserabilism. New research by consumer group Which? found that the average cost of a shopping bill is now £76.83 per week – an increase of £5.66 on the previous year.

Only three years ago, the UK government's chief scientific adviser, Sir John Beddington, warned that the world faced a "perfect storm" of food, water and energy problems, due to global warming and the rising global population. Elements of that perfect storm are here now. Doubters can read Damian Carrington's summary of recent scientific findings or read the study released by Munich Re, the world's largest reinsurance firm, which sees climate change driving increased weather volatility and predicts those influences will continue in years ahead.

It's clear we need to change the way we do food. We need to make food part of the solution not a growing part of the problem of climate change.

But we're in for a shock. Cheap food, artificially low cheap food, is going to come under attack. Our manipulated subsidy of sectors of food and farming (beef and dairy) will have to change if we want to retain that particular myth. The new food reality will hit a food economy that's already dysfunctional in terms of diet-related health, ecology (the food we eat accounts for 30% of the UK's carbon footprint) and social justice.

We're not going to like this. There's been an undercurrent of soft-denialism that goes something like this. The weather may be changing but it will be good for us here in northern Europe. It's most often heard around soft fruit or vineyards in "unusual places" and almost always has a gallows humour to it. I think we'll be hearing a lot less of this as the realities of globalised food and a fundamentally altered weather system come to the fore.

With this the notion of "bounty" or "plentitude" that's deeply imbedded in our understanding may be under challenge. The sense of entitlement wrapped up in a lovely jumble of pagan and Christian symbolism that used to roll together into a vague Thanksgiving will come under question. The cornucopia of living in a fertile land. Now we're more likely to expect ceaseless globalised food from the shelves of 24-hour Tescos. Unacknowledged, food just gushes out, endlessly. Doesn't it?

We may have broken the cycle of appreciation long ago and will simply wake up shocked and angry that we can't buy lots of very cheap food. That was our birthright, right? Like houses you could make money off or the certainty of banking, cheap petrol so you can drive anywhere, cheap food – the notion of abundance – is the next of our pillars of certainty about to be knocked away.

What can we do? We may have to change our thinking about how we do food and farming in response to climate change from one of mitigation to adaptation. We definitely will have to change our model of farming from one of vast mono-crop farms which are heavily dependent on external inputs and highly vulnerable to failure, to more diverse and smaller scale models. That has huge consequences for land ownership, tenancy, planning law and urban agriculture. We'll have to look at much shorter supply chains using less energy and routes and networks that are far less vulnerable to failures and shocks through the system than our vast over-extended globalised food system.

We should abandon "yield" as the sole metric of farming success. It has its twin in the concept of "growth" that has driven western economics to ruin. There are other things we can do to drastically reduce waste. We can eat "ugly food", we can stop subsidising biofuels, and we can begin the slow process of wrestling the food system back from big farming, the multiples and the handful of companies that dominate our broken food system. Diversity, open source farming and food sovereignty is the key. It's harvest time, but it's going to cost us all.